1. Field of the Invention
The present invention relates to a method of adjusting the sensitivity of and stabilizing an optronic fuse system, which possesses a controller and an avalanche photodiode (APD) constituting a receiver.
2. Discussion of the Prior Art
Optronic fuse systems are known per se in various configurations. For example, German Patent No. DE 24 56 162 C2 discloses a missile fuse with an opto-electronic measuring device, which, upon reaching a given range between the missile and a target surface, delivers a signal to an evaluation circuit. That known measuring device has a transmitter which emits optical pulses at a pulse repetition frequency through a lens and a receiver which is arranged at a given spacing from the transmitter and which records portions of those optical pulses, which are returned from the target surface by way of a further lens, with a narrow-band-pass filter which is tuned to the pulse repetition frequency, and a receiving amplifier. In order to eliminate the effects of circuitry-induced frequency deviations, connected between the band-pass filter and the transmitter is a regulating circuit by means of which the pulse repetition frequency of the transmitter tracks the center frequency of the band pass filter. The input signal of the regulating circuit is a signal, which is filtered out of the noise level of the receiving amplifier by the band pass filter.
An optical range sensor for a missile fuse is described in German Patent No. DE 26 08 066 C2, which operates on the basis of the pulse reflection principle and which in the reception branch thereof has in series connection of an amplifier, a gate circuit, which is opened in the transmission pulse cycle, an integrating capacitor circuit and a threshold switch. Arranged in the reception branch of that optical range sensor, upstream of the gate circuit, is a high-pass filter whose limit frequency is slightly below the transmission pulse repetition frequency. The integrating capacitor circuit is connected in such a way that it sums positive and negative signal components in accordance with the sign thereof.
An adjusting device located on opto-electronic proximity fuses is known from the disclosure of German Patent No. DE 27 14 766 C2 wherein, arranged in mutually juxtaposed relationship in the head of the fuse, are the optical systems of a transmitter provided with a directional antenna or emission device of a small area, and a light receiver is provided with a radiation detector which is also of a small area in size, whose light characteristics which are afforded by optical lenses can be adjusted in such a way that the beams thereof cross at a reference or target distance from the fuse head. In that case, the beam transmitter and the beam receiver are each arranged on a respective slider, which is disposed so as to be transversely displaceable on a disc-shaped carrier plate. The two carrier plates for the respective sliders are, in turn, supported in mounting bodies, which are each rotatable about the optical axis of the associated lens, which extends through the associated carrier plate and can be arrested after adjustment has been effected.
German Patent No. DE 39 18 243 C2 discloses an optronic proximity fuse, which responds to a reflection amplitude being exceeded and which has an adjustable mechanical aperture member in its beam path, which is to be reflected at a target surface, comprising transmission and reception characteristics. The aperture member is designed for triggering a fine threshold adjustment or calibration after coarse adjustment of the transmitter and the receiver, and is in the form of a pin-shaped shading element, which engages transversely with respect to the beam path to a greater or lesser depth into one of the characteristics. Moreover, an optronic fuse, which is designed in particular for a large-caliber aerial bomb is described in German Patent No. 39 27 819 C2.
Furthermore, Lau, et al., U.S. Pat. No. 4,153,835, describes an analog circuit, which facilitates a precise following of an operating voltage to a temperature dependent breakdown voltage within a temperature range of 0° C. through 50° C. This, in effect, pertains to a temperature compensation circuit, which in no manner can be employed to implement the inventive method of adjusting an optronic fuse system.
Nourrcier, Jr., U.S. Pat. No. 5,638,163, similar to the Lau, et al. patent, merely describes the implementation in a regulation of the operating voltage. However, the goal described in that particular publication is always to be able to set the best s/n ratio (signal to noise ratio) that is achieved, and wherein the operating voltage is increased for so long until the noise leads to sporadic distance measurements (the transmitter is not activated). In effect, the setting or adjustment criteria is the CFAR threshold, for example, the measurement of five erroneous measurements per second or the like. This has nothing in common with the present invention.
The object of the present invention is to provide a method of the kind set forth in the opening part of this specification, in which manual adjustment or calibration is eliminated so that the optronic fuse system, that is to say the optronic proximity fuse, is possible with a design which is appropriate for the demands of manufacturing